This campaign might, of course, be called merely a part of Venice’s commercial policy, defence not aggression; but later, in 1423, the Florentines persuaded the Republic to join with them in a war against the Visconti, declaring that they were weary of struggling alone against such tyrants, and that if Venice did not help them they would be compelled to make Filippo Maria ‘King of North Italy.’ The result of the war that followed was a treaty securing Venice a temporary increase of power on the mainland, and may be taken as the first decisive step in her deliberate scheme of building up a land-empire in Italy. Machiavelli, a student of politics in the sixteenth century, who wrote a handbook of advice for rulers called _The Prince_, as well as the history of Florence, his native city, declares that the decline of the Venetians ‘dated from the time when they became ambitious of conquests by land and of adopting the manners and customs of the other states of Italy’. This may be true; but it is doubtful whether the great Republic could have remained in glorious isolation with the Visconti knocking at her gates. * * * * * [Sidenote: Florence] From Venice we must turn to Florence, which, by the fifteenth century, emerged from petty rivalries as the first city in Tuscany. Like Milan, Florence fell a prey to Guelfs and Ghibellines; but these feuds, instead of becoming a family rivalry between would-be despots, developed into a bitter class-war. On the fall of Frederick II the Guelfs, who in Florence at this date may be taken as representing the _populo grasso_, or rich merchants, as opposed to the _grandi_, or nobles, succeeded in driving the majority of their enemies out of the city. They then remodelled the constitution in their own favour. The chief power in the city was now the ‘Signory’, composed of the ‘Gonfalonier of Justice’ and a number of ‘Priors’, representatives of the _arti_, or guilds of lawyers, physicians, clothiers, &c.: to name but a few. No aristocrat might stand for any public office unless he became a member of one of the guilds, and in order to ensure that he did not merely write down his name on their registers it was later enacted that every candidate for office must show proof that he really worked at the trade of the guild to which he claimed to belong.